[Sonographic diagnosis of hip dysplasia. Principles, sources of error and consequences].

Sonography of the hip in infants is being increasingly employed. This method of examination involves several specialist disciplines. The more widespread its use, the greater the likelihood of faulty diagnoses if one is not aware of its weak points. Faulty diagnoses are the order of the day if the method is employed by persons whose knowledge has not been updated to latest advances in the field; other sources of error are faulty scanning, unsuitable sonographic equipment and insufficient documentation. Hence, it is mandatory to describe the demands to be made on the equipment according to update standards and to draw up guidelines that will help to avoid quality loss. The criteria for assessing a hip sonogram are defined and the problem of age limit is considered. A review is given of disturbances of normal development of the hip. The possibility of effecting dynamic examination should not mislead one to neglect assessment of the hip joints as precisely as possible by means of an exacting measurement technique. The weak points of the technique of measurement and the valuation of the angles must be known. A review of the literature reveals many problems in hip sonography. A multitude of these problems is unnecessary and can be considered as solved if one would try to match modern quality demands and not be satisfied with a quality standard that is many years old. To achieve best possible hip examination via sonography it will often be necessary to considerably modify principles of general sonography of the soft parts.